August 2012

Creature Comforts

Cricket talk.

Anita Carpenter

Enjoy the cricket talk now. Love-lorn male field crickets began chirping on warm July nights. Theirs was just one of many voices in the insect chorus. But when the cool fall evenings arrive, only the slow deliberate chirps of field crickets will remain to fill the stillness.

Crickets are more often heard than seen. Each male selects a favorite secretive spot: in the lawn, along the sidewalk, in a stone wall crack, within a woodpile, under a porch or inside a garage. There, he defends his territory, passionately and incessantly, chirping night after night, waiting for a female cricket to arrive.

Crickets are relatives of grasshoppers, locusts and katydids – all belonging to the insect order Orthoptera. Taxonomically separated from the others, crickets belong to their own family, the Gryllidae, and field crickets have their own subfamily – the Gryllinae.

The familiar chirper is the northern field cricket, Gryllus pennsylvanicus. If one of these field crickets should jump into your path, the ½- to ¾-inch black insect with the squarish head and thorax would be instantly recognized. Each cricket has two long tapering antennae, which are longer than its body. The many-segmented antennae are constantly in motion, touching and sensing. Two spinelike projections extend up at a 30-degree angle from the field cricket's abdomen. These enlarged cerci give the insect an armored appearance.

Of the three pairs of black legs, field crickets' hind legs are the largest and give the insect the spring in its leap. Field crickets are not graceful leapers and often land clumsily and off balance, sometimes ending with a not-so-perfect summersault. Crickets prefer to scramble along the ground. Adapted to a terrestrial existence, their hind legs are covered with spines that enable them to crawl and squeeze around grass stems. Crickets are not climbers and seldom, if ever, grasp grass blades as grasshoppers do.

Cricket wings are unique. The pair of blackish, hardened wings snugly covers the upper three-quarters of the abdomen much like a lid fits on an old-fashioned hat box. The base of the right wing overlays the left wing base. Insects typically have two pairs of wings. In field crickets, these stiff wings cover and conceal the vestiges of the second wing pair. In grasshoppers, locust and katydids, the second wing pair is well-developed and used for flight. Crickets can't fly.

Cricket wings give crickets their "voices." Crickets don't sing like birds do but produce a chirping sound by rubbing their wings together, a behavior known as stridulation. Only the wings of male field crickets are modified to produce sound. A thickened band covered with transverse ridges, called the file, runs horizontally across the base of the right wing. The scraper is a sharp edge located on the upper inside edge of the left wing.

When "singing," the cricket raises its wings to a 45-degree angle. The wings resonate, moving back and forth. With each closing motion, the scraper slides across the file on the underside of the upper wing, generating a high-pitched pulse lasting about 1/100 of a second. Three pulses in quick succession make up one chirp. The repetition of chirps comprises the cricket song, which is musical and can be assigned a pitch. Chirp rate is dependent on temperature. A field cricket song influenced by August's heat is much faster than one produced in late September's coolness.

Each cricket species produces its own song, which may differ in pitch, pulse rate and/ or varying intervals between chirps. Female crickets can differentiate from among the various songs and select the appropriate male.

It would do little good for field crickets to spend so much time "singing" if other crickets couldn't hear it. Crickets can hear but not with ear drums located on their heads. Crickets hear with their legs. The tympanum is visible as a small white oval located on the tibia of each front leg.

Female field crickets can easily be identified from males by the presence of a long cylindrical ovipositor which extends 5/8 of an inch (almost equal to her full body length) beyond her abdomen. She uses her ovipositor to deposit eggs in soil. The eggs overwinter and hatch into nymphal crickets the following spring. Dining on plants, the nymphs grow and molt three to four times, reaching adulthood in late July. Then the cricket serenade begins.

As one of the few sounds of late summer and early autumn, cricket music surrounds us but it quickly fades from our consciousness. Tune into the cricket talk and enjoy the soon-to-be-silent autumn serenade.

Anita Carpenter enjoys the cricket serenade around her home in Oshkosh.